Unit 5: Gases
Study List
Measuring Pressure
 Know the pressure of the atmosphere at sea level measured in atm, kPa, mmHg, torr,
psi
 Convert one pressure unit into another
 Understand how to measure pressure using a U-tube manometer, open-end
manometer, and a barometer
Recognizing Graphs
 Recognize from a graph whether two variables are directly or inversely proportional.
 Manipulate a curve graph to give a straight-line graph
 Form a mathematical law from a straight-line graph
Sketch graphs for the following: P vs. V, V vs. 1/P, V vs. T
Ideal Gas Law
 Know the Ideal Gas Law and assumptions we make about gases
 Given the molar volume of a gas (22.414 L at STP) determine values of R, the ideal
gas constant, with different pressure units
 Do Ideal Gas Law problems
Twists on the Ideal Gas Law
 Derive the gas density equation from the Ideal Gas Law
 Do gas density problems
 Calculate molar mass from P, V, and T data
Stoichiometry
 Do Gas Laws and Stoichiometry problems by determining mass or moles of a
substance (1 mol = 22. 4 L)
Dealing with Mixtures of Gases
 Know Dalton’s Law of Partial Pressures
 Do Partial Pressure problems
 Apply this to gases collected over water
Explaining the Gas Laws
 Know the principal features of the Kinetic Molecular Theory of gases
 Be able to explain why each of the gas laws works in terms of the Kinetic Molecular
Theory
Why Do All Gases Act The Same?
 Derive Graham’s Law of Effusion from rms or KE of two gases
 Do Graham’s Law problems
How do real gases differ from ideal gases?
Unit 5: Gases
Study List
1) A hydrogen gas thermometer is found to have a volume of 100.0 cm3 when placed in
an ice-water bath at 0°C. When the same thermometer is immersed in boiling liquid
chlorine, the volume of hydrogen at the same pressure is found to be 87.2 cm3. What is
the temperature of the boiling point of chlorine?
A: 238 K (-35°C)
2) 2.50 g of XeF4 gas is placed into an evacuated 3.00 liter container at 80°C. What is the
pressure in the container?
A: 0.117 atm
3) 6.2 liters of an ideal gas are contained at 3.0 atm and 37 °C. How many moles of this
gas are present?
A: 0.75 mol
4) Hydrogen gas is collected over water at 24°C. The total pressure of the sample is 755
mm of mercury. At 24°C, the vapor pressure of water is 50 mm of mercury. What is the
partial pressure of the hydrogen gas?
A: 705 mm Hg
5) You decide to go on a long hot air balloon ride, so you decide to bring some shampoo
to wash your hair with. However there is some gas inside the shampoo bottle when you
start to climb into the basket at the beginning of your journey. In fact, because you are a
good scientist you decide to constantly take measurements of your surroundings. The
shampoo bottle contains 435ml of gas, under a pressure of 1.10 atm, at a temperature of
30.0°C. When you climb high into the air the bottle starts to expand eventually exploding
and covering you and your companions with Pert Plus. Eager to explain this phenomenon
you take some measurements: the pressure, you note, has dropped to 0.734 atm and the
temperature has dropped to 5.00°C. To what new volume did the gas inside the bottle
expand?
A:598 mL
How do hot air balloons rise?!
6) If you were to take a volleyball scuba diving with you what would be its new volume
if it started at the surface with a volume of 2.00L, under a pressure of 752.0 mmHg and a
temperature of 20.0°C? On your dive you take it to a place where the pressure is 2943
mmHg, and the temperature is 0.245°C.
A: 0.477 L
7) A sample of CH4 is confined in a water manometer. The temperature of the system is
30.0 °C and the atmospheric pressure is 98.70 kPa. What is the pressure of the methane
gas, if the height of the water in the manometer is 30.0 mm higher on the confined gas
side of the manometer than on the open to the atmosphere side. (Density of Hg is 13.534
g/mL).
A: 94.2 kPa.
Unit 5: Gases
Study List
8) A mixture of nitrogen and neon gases contains equal moles of each gas and has a total
mass of 10.0 g. What is the density of this gas mixture at 500 K and 15.0 atm? Assume
ideal gas behavior.
A: 8.81 g/L
9) Three 1.00 L flasks at 25.0 °C and 1013 kPa pressure contain: CH4 (flask A), CO2
(flask B) and NH3 (flask C). Which flask (or none) contains 0.041 mol of gas? Which gas
behaves most ideally? Which gas has the lowest velocity?
Answer: All three flasks contain 0.041 mol of the different gases. CH4 behaves most
ideally (less polar). CO2 has the lowest velocity.
10) 1.0 L of liquid nitrogen is kept in a closet measuring 1.0 m by 1.0 m by 2.0 m.
Assuming that the container is completely full, that the temperature is 25.0 °C, and that
the atmospheric pressure is 1.0 atm, calculate the percent (by volume) of air that would
be displaced if all the liquid nitrogen evaporated. (Liquid nitrogen has a density of 0.807
g/mL.)
A: 35.2% of the air gets displaced.
11) The vapor pressure of solid iodine at 30.0 °C is 0.466 mmHg.
a. How many milligrams of iodine will sublime into an evacuated 1.00 L flask?
b. If 2.00 mg of I2 are used, what will the final pressure be?
c. If 10.00 mg of I2 are used, what will the final pressure be?
A:
a. To 3 significant figures, this is 6.26 mg.
b. P = 1.96 x 10¯4 atm (or 0.149 mmHg)
c. The pressure would be 0.466 mmHg. Remember that vapor pressure is an equilibrium
process. At 0.466 mmHg there would be established an equilibrium between I2(s) and
I2(g). There would be 3.74 mg of solid I2 remaining in the flask.
12) 1 mole each of He gas and CO2 gas are in a rigid container at the same temperature.
The kinetic energy of He is ________________ (greater than, less than, the same as) the kinetic
energy of CO2?
The velocity of He is ________________ (greater than, less than, the same as) the velocity of
CO2?
Calculate the ratio of the velocities of He/CO2.
Unit 5: Gases
Study List
When HCl(g) and NH3(g) come in contact, they form a white solid, NH4Cl(s).
If samples of the two gases are placed at the ends of a tube, the white solid will appear closest
to point ___?
HCl
a
b
c
d
e
NH3
13) Consider the following changes imposed upon a sample of gas, assuming the variables not
mentioned remain constant:
a. What happens to the pressure if the temperature in K is doubled?
b. What happens to the volume if the pressure is tripled?
c. What happens to the volume if the temperature decreases from 300K to 200K?
d. What happens to the temperature if one-half of the gas is removed?
e. What happens to the pressure if volume decreases from 4 Liters to 2 Liters and the
temperature increases from 25C to 323C?
14)